CATALYZERS OF GROWTH 



507 



The influence of tethelin upon the growth of mice is therefore 

 similar to the effect of administering cholesterol, save that results are 

 attained by administration of tethelin with a tenth of the dosage that 

 would be requisite in the case of cholesterol. It is very significant, 

 therefore, that the action of tethelin upon inoculated Carcinoma in 

 rats again reproduces the effects of cholesterol (Fig. 42.) 



Even more striking than its effect upon the growth in weight of the 

 animals is, however, the effect of tethelin upon the general contour 

 and appearance of mice to which it has been administered continuously. 

 The tethelin-fed animals are remarkably robust and compact in build. 

 Weight for weight they are smaller and size for size much heavier than 

 normal animals. The contours of their surface are more rounded and 

 fully adult animals retain a youthful appearance which is soon lost in 



80- 



60- 



4-0 



20- 



Per cent Increase over 

 Diameter at 21 days 



Days after inoculation 



21 



23 



25 



28 



30 



FIG. 42. The acceleration of the growth of carcinomata (in rats) by hypodermic 

 administrations of tethelin. 



normal animals. The coats of the males, even at fourteen, months of 

 age, retain the glossy, silky appearance of the coats of young animals 

 or of females, while six months or more prior to this age the coats 

 of normal males are already shaggy, staring, and discolored. These 

 differences are clearly displayed in the accompanying photograph, 

 in which a normal and a tethelin-fed male of the same age (one year) 

 and of the same weight (28.0 gm.) are compared (Fig. 43). The 

 normal animal on the left has a shaggy, staring and discolored coat, 

 while the tethelin-fed animal has a smooth, glossy and pure white coat. 

 The normal animal is irregular in outline and loosely built, while the 

 contour of the tethelin-fed animal is rounded and its build is compact. 

 In each of these three instances of growth-catalysis, therefore, we 

 meet with the apparently contradictory fact that while the growth of a 



